package RSA;

import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

public class RSA {

    public static Map<Integer,String> map = new HashMap<>();


    /**
     * 随机生成密钥对
     *
     * @throws NoSuchAlgorithmException
     */
    public static String getPublicKey() throws NoSuchAlgorithmException {
        // 将公钥和私钥保存到Map
        return map.get(1);
    }

    public static String getPrivateKey() throws NoSuchAlgorithmException {
        // 将公钥和私钥保存到Map
        return map.get(0);
    }

    private static void genarateKeyPair() throws NoSuchAlgorithmException {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        keyPairGen.initialize(1024, new SecureRandom());
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();   // 得到私钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  // 得到公钥
        String privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));
        String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
        map.put(0,privateKeyString);
        map.put(1,publicKeyString);
    }


    /**
     * RSA公钥加密
     *
     * @param str       加密字符串
     * @return 密文
     * @throws Exception 加密过程中的异常信息
     */
    public static String encrypt(String str,String publicKey) throws Exception {
        //base64编码的公钥
        byte[] decoded = Base64.decodeBase64(publicKey);
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
        //RSA加密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        String outStr = Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));
        return outStr;
    }

    /**
     * RSA私钥解密
     *
     * @param str        加密字符串
     * @return 铭文
     * @throws Exception 解密过程中的异常信息
     */
    public static String decrypt(String str,String privateKey) throws Exception {
        //64位解码加密后的字符串
        byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
        //base64编码的私钥
        byte[] decoded = Base64.decodeBase64(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));
        //RSA解密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        String outStr = new String(cipher.doFinal(inputByte));
        return outStr;
    }

    public static void main(String[] args) throws Exception{
        RSA.genarateKeyPair();
        String aaa = RSA.encrypt("aaa", RSA.getPublicKey());
        System.out.println(aaa);
        System.out.println(RSA.getPublicKey());
        String decrypt = RSA.decrypt(aaa,RSA.getPrivateKey());
        System.out.println(decrypt);
    }

}

